Inflammatory arthritis is a prominent clinical manifestation in diverse autoimmune disorders including rheumatoid arthritis (RA), psoriatic arthritis (PsA), systemic lupus erythematosus (SLE), Sjogren's syndrome, and polymyositis. Most patients with these diseases develop joint deformities on physical examination, but typically only RA and PsA patients manifest bone erosions on imaging studies.
RA is a chronic inflammatory disease that affects approximately 0.5 to 1% of the adult population in northern Europe and North America, and a slightly lower proportion in other parts of the world. It is a systemic inflammatory disease characterized by chronic inflammation in the synovial membrane of affected joints, which ultimately leads to loss of daily function due to chronic pain and fatigue. The majority of patients also experience progressive deterioration of cartilage and bone in the affected joints, which may eventually lead to permanent disability. The long-term prognosis of RA is poor, with approximately 50% of patients experiencing significant functional disability within 10 years from the time of diagnosis. Life expectancy is reduced by an average of 3-10 years. Patients with a high titer of rheumatoid factor (RF) (approximately 80% of patients) have more aggressive disease, with a worse long-term outcome and increased mortality over those who are RF negative.
A common problem in caring for patients with rheumatoid arthritis is the inadequacy of current disease markers to individualize the assessment of prognosis. This is important because this inflammatory autoimmune disease often leads to chronic pain, impaired quality of life, disability, extra-articular complications and comorbidity, and increased mortality. Various approaches of predicting how patients will fare long-term have been evaluated over the years; while several have been found to be informative at the population level, few, if any, have proved sufficiently predictive at the level of individual patients to justify use in clinical practice.